An ingredient in a common cold medicine produced a psychotic episode in a mentally troubled engineer that led him to slash the throats of his two children, a doctor testified at the man's murder trial.

Dr. James O'Brien, a toxicology expert at the University of Connecticut, said Monday that the ingredient, phenylpropanolamine, would not itself cause such a reaction, but it aggravated Brian Bibb's paranoia and depression."PPA was the straw the broke the camel's back," O'Brien said.

Bibb, a 32-year-old former Texaco Inc. engineer, has pleaded innocent by reason of insanity to charges of murdering his children, ages 2 and 5, at their suburban New Orleans home June 3.

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